DataContact
A datacontract is formal agreement between a client and service that abstractly describe the data to be exchanged. In wcf, the most common way of serialization is to make the type with the datacontract attribute and each member as datamember.

Properties of DataMember:EmitDefaultValue: We can set default value in .net framework. We can set default value in datamember. We can achieve this by using EmitDefaultValue property. By default it is false.